The handle of a hand tool such as a screwdriver is for a user to hold and exert force onto the hand tool. Accordingly, the configuration of the handle determines the holding effect and force application effect of a user when operating the hand tool.
Different users have different sizes of palms and different lengths of fingers. The conventional handle is generally designed without taking into consideration that different users have different sizes of hands.
The conventional handle generally has a symmetrical configuration. U.S. Pat. No. 3,173,462 discloses a grip 12 of a screwdriver. The body portion of the grip 12 has six longitudinal grooves 22. Six small grooves 24 are formed on a periphery of a front end of the grip for a user to quickly rotate the tool by finger movement. The small grooves 24 on the front half of the grip and the longitudinal grooves 22 of the rear half of the grip have the same number to form a symmetrical configuration.
U.S. Design Pat. No. D510,692 discloses a grip having a body portion and a front neck portion. Four grip faces are disposed on the body portion and four abutment faces are disposed on the neck portion. The grip faces and abutment faces also form a symmetrical configuration.
U.S. Design Pat. No. D328,700 discloses a grip having a front half and a rear half, which are symmetrically arranged. As shown in FIGS. 1 to 6 of this Design Patent, four elongated wide grooves are disposed on a front half of the grip, while eight elongated narrow grooves are disposed on a rear half of the grip. As shown in FIGS. 7 to 12 of this Design Patent, three wider grooves are disposed on the front half of the grip, while six narrower grooves are disposed on the rear half of the grip. The front half and the rear half of the grip also form a symmetrical configuration.
As exemplified with said U.S. Design Pat. No. D510,692, a user's palm and four fingers together hold the body portion of the grip with the thumb pressing against an abutment face. Accordingly, the grip provides more force application points to achieve better holding effect. However, the grip has fixed size and is suitable only for a certain size of hand. To those users with larger hands or smaller hands, it is hard to firmly hold the grip. As the grip has a symmetrical configuration with fixed holding range, wherever a user holds the grip, that is, when a user turns the grip 90-degree clockwise or counterclockwise and then hold it with his/her hand, no matter where the user holds the grip, the holding range for the hand will be exactly the same with no difference. Therefore, the symmetrical grip is only adapted to common-size hands, while being unsuitable for otherwise sized hands.
In U.S. Design Pat. No. D328,700, there are four wide grooves disposed on the front half of the grip for a thumb to press against any of the wide grooves. In U.S. Design Pat. No. D510,692, there are four abutment faces disposed on the neck portion of the grip for a thumb to press against any of the abutment faces. However, in U.S. Pat. No. 3,173,462, there are six small grooves 24 disposed on the front end of the grip to define six protruding sections between the small grooves. The small grooves are not for the thumb to press against. This is because each small groove has a width too small for the thumb to contact. Instead, the thumb contacts the protruding section. When applying force to the grip to rotate the same, a user will not press his/her thumb against the front end of the grip. This is because in this case, the user's thumb will feel painful.
U.S. Pat. No. 3,586,080 discloses a handle 1 of a screwdriver. The handle 1 has a rear portion 3 on which three grip regions 10 are disposed. Eight small longitudinal grooves 6 are disposed on a circumference of a front end of the handle 1. The number of the small longitudinal grooves 6 of the front end is different from the number of the grip regions 10 of the rear portion 3. The small longitudinal grooves 6 and the grip regions 10 are such arranged as to form an asymmetrical configuration. However, the small longitudinal grooves 6 are not for the thumb to press against. This is because in the case that a user presses his/her thumb against the front end of the handle, the user's thumb will feel painful.